Cytoskeleton of rat neoplastic cells of spontaneous origin and their derivatives after supertransformation with avian sarcoma virus B77 in vitro.

Changes in the distribution of actin-containing cables (microfilament bundles), microtubules and fibronectin were studied by immunofluorescence in four rat neoplastic cell lines and compared with those of normal rat fibroblasts. No changes in the organization of microtubules were seen. A network of fibronectin filaments was observed only in normal fibroblasts whereas a few short fibronectin fibres were observed in cultures of all tumour cells. The actin-containing microfilament bundles in LW13K2 fibroblasts transformed spontaneously in vitro were shorter and differed in their orientation from those of normal fibroblasts. Almost no changes in action distribution in the supertransformed K2B773 cells, compared to LW13K2 cells, were observed. Absence of the actin-containing microfilament bundles, or only a few thin bundles were seen in cells of a spontaneous mammary carcinosarcoma SAM-LEW. Actin cables increased in thickness and number in the B77-supertransformed SAMB774 cells. The effect of pp60src on the organization of actin in neoplastic cells as compared to normal cells is discussed.